1. Field of the Invention
The present invention relates to a rear projector, and more particularly, to a rear projector that can adjust both the size of the image that it displays, as well as its mode of operation.
2. Description of the Prior Art
When displaying images from different digital sources, the size of the image displayed on a prior art rear projector will change based upon the resolution of the image. Please refer to FIG. 1. FIG. 1 is a diagram of the different sizes of an image displayed at various resolutions. The most common resolutions in use are SVGA (800xc3x97600), XGA (1024xc3x97768) and SXGA (1280xc3x971024). As SVGA has the lowest resolution, it appears on the prior art rear projector with the smallest image size. In order to fill the entire display area, the SVGA image must be enlarged. This is usually done digitally by interpolating extra pixels to simulate the higher resolution image. This method, however, can easily lead to distorted images.
It is therefore a primary objective of the present invention to provide a rear projector that adjusts image size and its operating method to solve the above mentioned problem.
In a preferred embodiment, the present invention provides a rear projector having a housing, a screen installed in the front of the housing for displaying an image, a projecting module installed in the housing, a control module, and at least one detector. The projecting module includes an image generator that converts image signals into an image with a corresponding resolution, and a projecting lens set used for projecting the image onto the back of the screen. The control module is used for controlling the projecting module, and when the control module receives a focus-changing signal, the control module will change the focus of the projecting lens set to adjust the size of the image. The detector is installed at a predetermined position on the screen for sensing the image on the screen, and the detector is electrically connected to the control module. When the control module receives the focus-changing signal, the control module will continuously change the focus of the projecting lens set to adjust the size of the image until the detector senses the edge of the image.
It is an advantage of the present invention that, by adjusting the focus of the projecting lens set, images at various resolutions can be optically adjusted to fit to the screen. This avoids the prior art problem of image deviation caused by digital interpolation.
This and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiment, which is illustrated in the various figures and drawings.